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One Way Ratchet

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MOST Delta filament as guide.JPG This page was part of an MTU course MSE4777 OA and MSE4777 OB/MSE5777/EE4777/EE5777: Open-source 3-D printing

Please leave comments using the discussion tab. The course runs in the Fall semester. It is not open edit.


One Way Ratchet[edit]

Project developed by Wedallma 
Status
This OSAT has been designed but not yet tested - use at own risk.
This OSAT has been prototyped.

You can help Appropedia by contributing to the next step in this OSAT's status.

Abstract[edit]

  1. The ratchet is a fairly common tool in today's world. A major advantage of a ratchet is that many tool attachments can be put on the ratchet to perform many different functions. One issue with the ratchet though is that it can oftentimes be very costly to buy one. A printable ratchet could drastically reduce the cost for those in need of tools, such as third world countries. Additionally, the ratchet gives the option of being able to cheaply print any tool attachment that is needed, instead of having to pay for the many different kinds of tools that are available.
  2. For this project I used Blender to create each part.
Fully Assembled Ratchet
Top view of ratchet  
Front view of ratchet  
Back view of ratchet  

Bill of Materials[edit]

  1. The full BOM is as follows:
    1. The ratchet outline is 14 grams in weight and 4.57 meters in length. The approximate cost of this part is $0.42.
    2. The ratchet cover is 3 grams in weight and 1.07 meters in length. The approximate cost of this part is $0.09.
    3. The ratchet gear is 5 grams in weight and 1.76 meters in length. The approximate cost of this part is $0.15.
    4. The gear pin is 0 (too small to even be 1 gram) grams in weight and 0.06 meters in length. The approximate cost of this part is $0.01.
  2. Files
    1. The Blender source files and STLs can be downloaded here: One Way Ratchet Thingiverse. Additionally the STL files can be downloaded from below.
    2. File:Ratchet.stl
    3. File:RatchetGear.stl
    4. File:GearPin.stl
    5. File:RatchetCover.stl

Tools needed for fabrication of the OSAT[edit]

  1. MOST Delta RepRap or similar RepRap 3-D printer
  2. Depending on print quality, a knife may be needed to shave away plastic on the edges of the parts that come together.
  3. Super glue may be needed to join the gear pin to the ratchet to add reliability, though super glue is not entirely necessary for the ratchet to function.

Skills and Knowledge Necessary to Make the OSAT[edit]

  • No special skills or knowledge needed.

Technical Specifications and Assembly Instructions[edit]

  1. First, take note that there is a small opening and a large opening on the ratchet. Inside the large opening is a small rectangular inlet, this is where the gear pin is placed. As mentioned in the "Tools needed..." section above, super glue can be placed on the gear pin and inlet to attach the gear pin to the ratchet. Next, the block on the ratchet gear is placed through the small opening of the ratchet starting from the large opening. Lastly, the ratchet cover is placed over the large opening of the ratchet to cover up the parts inside the ratchet.
  2. The small opening on the ratchet may need to have some plastic shaved away (by a knife or similar tool) for the gear to move properly inside the ratchet. Additionally, the ratchet cover may need to have some plastic shaved away (by a knife or similar tool) to fit on the backside of the ratchet.
  3. Total print time estimate is 152 minutes. Print time estimates for the individual parts are as follows: ratchet - 89 minutes, ratchet cover - 16 minutes, ratchet gear - 43 minutes, and gear pin - 4 minutes.
  4. Assembly time estimate of less than 5 minutes. If using super glue on the gear pin, assembly time is increased by the amount of time the glue needs to set.
Unassembled Ratchet
All four parts to build the ratchet  

Common Problems and Solutions[edit]

  • One primary problem with this ratchet is that it is only one way, in other words, the ratchet direction cannot be switched between clockwise or counter-clockwise. At this moment, the ratchet functions in a counter-clockwise direction. The only solution is to print a second ratchet that can function in the clockwise direction. To do this, the ratchet and ratchet gear STLs simply need to be mirrored to create a clockwise ratchet. The gear pin and ratchet cover do not need to be mirrored since they are symmetrical and do not affect the direction of the ratchet.
  • It's important to note that this is a ratchet without any attachments. Tool attachments can be made to fit the 12mm x 12mm block end of the gear.

Cost savings[edit]

  1. The total cost estimate of the ratchet is $0.67. Since two ratchets are needed to complete the function of a factory manufactured ratchet, the total cost of both ratchets is $1.34.
  2. A commercial ratchet at the very lowest price costs about $12.00.
  3. Total savings = $10.66 at a 88.8% savings rate.

References[edit]

  1. Image: Wikimedia. Available: http://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Ratchet_Drawing.svg/180px-Ratchet_Drawing.svg.png